Spark plugs having multiple air gaps and employing resistors are known such as described in U.S. Pat. No. 4,004,562. In general, the air gaps are substantially equal in length and equal to the maximum or optimum gap for the engine. In operation, once current flows in a gap most of the voltage drop is across the resistor and only a small voltage drop occurs across the gap. Each gap receives the full voltage employed by the ignition system until current flows. Thus, the length of the gaps are made to be substantially the same and equal to the length of the gap of a single gap spark plug operating under the same conditions.
In U.S. Pat. No. 3,488,556, a teaser gap is employed to ionize some of the gases in the main gap, and consequently, to reduce the voltage required to initiate sparking in the main gap. This teaser or secondary gap is not intended to ignite the gases in the cylinder, although under heavy load conditions, it may do so.
As will be seen, the present invention provides novel variations of a multiple gap spark plug.